Motor vehicle transmissions, in particular electric vehicle transmissions

ABSTRACT

The invention relates to a motor vehicle transmission (6) comprising a drive input shaft (9), a drive output shaft (10), a first planetary gearset (P1), a second planetary gearset (P2), and a third planetary gearset (P3), where the drive input shaft (9) is provided for coupling to an electric machine (5). Furthermore, at least functionally a first shifting element (A), a second shifting element (B), and a third shifting element (C) are provided. In addition, the invention relates to a drive unit (4), a drive axle (3), and an electric vehicle.

RELATED APPLICATIONS

This application claims the benefit of and right of priority under 35 U.S.C. § 119 to German Patent Application no. 10 2022 200 615.1, filed on 20 Jan. 2022, the contents of which are incorporated herein by reference in its entirety

FIELD OF THE DISCLOSURE

The invention relates to a motor vehicle transmission, in particular an electric vehicle transmission, comprising a drive input shaft which is provided for connection to a drive machine, a drive output shaft, and a first planetary gearset, a second planetary gearset and a third planetary gearset, each of which has a first element, a second element and a third element in the form, respectively, of a sun gear, a planetary web, and a ring gear, wherein at least functionally a first shifting element, a second shifting element and a third shifting element are provided, and wherein the first element of the first planetary gearset is connected rotationally fixed to the drive input shaft and the second element of the third planetary gearset is connected rotationally fixed to the drive output shaft. In addition, the invention relates to a drive unit with a motor vehicle transmission as mentioned above, a drive axle and an electric vehicle.

BACKGROUND

In a drive-train of electric vehicles, a motor vehicle transmission is provided between an electric machine and drive wheels of the electric vehicle in order to transmit a drive movement of the electric machine to the drive wheels, particularly in the slow range. Besides single-gear transmissions, transmissions are also used in electric utility vehicles, where two or more gears can be engaged.

WO 2015/082166 A1 describes a drive unit for an electric vehicle, wherein the said drive unit combines an electric machine and a motor vehicle transmission. Besides three planetary gearsets, the motor vehicle transmission comprises a plurality of shifting elements by the selective actuation of which a drive input shaft and a drive output shaft of the motor vehicle transmission can be coupled to one another with various gears engaged between them. In this case the drive input shaft is connected rotationally fixed to a rotor of the electric machine. The planetary gearsets consist in each case of a first element, a second element, and a third element, of which one is in the form of a sun gear, one in the form of a planetary web, and one in the form of a ring gear. Of the elements of the planetary gearsets, one is connected rotationally fixed to the drive input shaft and thus also to the rotor of the electric machine, whereas another element is connected permanently and rotationally fixed to the drive output shaft.

SUMMARY

Starting from the above-described prior art, it is now the purpose of the present invention to provide a motor vehicle transmission with a compact structure, by means of which various gears can be obtained. In particular the said motor vehicle transmission should be suitable for use in a drive-train of an electric vehicle.

This objective is achieved with embodiments disclosed herein. The detailed description describes advantageous further developments of the invention. The present disclosure relates to a drive unit which comprises a motor vehicle transmission according to the invention. In addition, the present disclosure relates to a drive axle with such a drive unit. An electric vehicle including the drive unit is also disclosed.

According to the invention, the motor vehicle transmission comprises a drive input shaft provided for connection to a drive machine, a drive output shaft, and a first planetary gearset, a second planetary gearset and a third planetary gearset, each of which comprises a first element, a second element, and a third element in the form, respectively, of a sun gear, a planetary web, and a ring gear. Furthermore, at least functionally a first shifting element, a second shifting element, and a third shifting element are provided. Moreover, the first element of the first planetary gearset is connected rotationally fixed to the drive input shaft whereas the second element of the third planetary gearset is connected rotationally fixed to the drive output shaft.

In the context of the invention a “shaft” is understood to be a component that can rotate, by way of which a power flow can be transmitted between components, such that for that purpose if necessary an associated at least functionally provided shifting element has to be actuated. The shaft concerned can connect components axially or radially or even both axially and radially to one another. Thus, the shaft concerned can also be present as an intermediate element by way of which only a radial connection is produced.

In the context of the invention “axial” means an orientation in the direction of a central longitudinal axis of the transmission, parallel to which rotation axes of rotatable components of the transmission, in particular of the shafts of the transmission and the elements of the planetary gearsets, are arranged. Then, “radial” is understood to mean an orientation in the direction of the diameter of a respective component of the transmission.

In the motor vehicle transmission according to the invention the drive input shaft is provided in order to form a drive-side coupling to a drive machine. For that purpose, the drive input shaft in particular is provided with a connection point at which a coupling of the drive input shaft to the drive machine can be formed. The said coupling is located between the drive machine and the drive input shaft in such a form that in the assembled condition of the motor vehicle transmission there is always a fixed rotation speed ratio between a rotation speed of the drive input shaft of the motor vehicle transmission and a rotation speed of the drive machine. Thus, in the context of the invention, between the drive input shaft and the drive machine there can, if necessary, be provided at least one further transmission ratio step, such as a spur gear step and/or a planetary step, by way of which a pre-transmission ratio of a rotation movement of the drive machine to the drive input shaft can be obtained. Particularly preferable, however, the drive input shaft of the motor vehicle transmission according to the invention is connected to the drive machine in a rotationally fixed manner so that the drive machine and the drive input shaft rotate at the same rotation speed.

The motor vehicle transmission in particular is a transmission for an electric vehicle and is designed to be connected by way of the drive input shaft to a drive machine in the form of an electric machine. As described above, a rotor of the electric machine can be coupled via at least one intermediate transmission ratio step to the drive input shaft of the transmission. Particularly preferable, however, in the assembled condition of the motor vehicle transmission, according to the invention, a rotor of the electric machine is connected directly to the drive input shaft in a rotationally fixed manner.

In the motor vehicle transmission according to the invention, the drive input shaft and the drive output shaft in particular are arranged coaxially with one another, and also preferably the planetary gearsets too are positioned coaxially with the drive input shaft and the drive output shaft. In that way the structure of the motor vehicle transmission can be made particularly compact in the radial direction.

The planetary gearsets consist in each case of a first element, a second element, and a third element, such that the elements of the individual planetary gearsets are in each case a sun gear, a planetary web, and a ring gear, respectively. Particularly preferable, the individual planetary gearsets are minus-planetary gearsets, in which the respective planetary web carries at least one rotatable planetary gearwheel which meshes both with the associated sun gear and with the associated ring gear. Thus, when the planetary gearsets are minus-planetary gearsets, then in particular the first element of the planetary gearset concerned is its sun gear, the second element of the planetary gearset concerned is its planetary web, and the third element of the planetary gearset concerned is its ring gear.

Alternatively, in principle, one or more of the planetary gearsets could be made as a plus-planetary gearset. In that case, on the planetary web concerned at least one pair of planetary gearwheels is mounted to rotate, of which planetary gearwheels one meshes with the associated sun gear and one with the associated ring gear. Moreover, the planetary gearwheels of the at least one planetary gearwheel pair mesh with one another. Otherwise than in a minus-planetary gearset design, the first element of the planetary gearset concerned is preferably the sun gear, the second element of the planetary gearset concerned is the ring gear, and the third element of the planetary gearset concerned is the planetary web. Compared with a minus-planetary gearset design, a stationary gear ratio of the planetary gearset concerned also has to be increased by one. As already described earlier, however, in the context of the invention, all the planetary gearsets are preferably minus-planetary gearsets. It is also preferable in the electric vehicle transmission according to the invention to provide exactly three planetary gearsets.

The motor vehicle transmission according to the invention comprises, at least functionally, a first shifting element, a second shifting element, and a third shifting element, by the selective actuation of which, in particular, different gears between the drive input shaft and the drive output shaft can be obtained. Particularly preferable, in the motor vehicle transmission according to the invention, in terms of their function, exactly three shifting elements are provided, such that by means of these shifting elements exactly three different gears can then preferably be obtained between the drive input shaft and the drive output shaft. In principle, however, within the scope of the invention, besides the first, second, and third shifting elements one or more further shifting elements could be provided, at least functionally.

That a particular shifting element is provided “at least functionally” means, in the context of the invention, that in the motor vehicle transmission according to the invention at least the respective function of the shifting element concerned is reproduced. In this, the shifting elements can specifically be physically present as individual shifting elements, or their function is reproduced by some other component such as a shifting device. A component that reproduces the said function can then combine the functions of two or more shifting elements in a single device.

The invention now incorporates the technical principle that the third element of the first planetary gearset and also the third element of the third planetary gearset are in each case immobilized. Furthermore, the second element of the first planetary gearset and the first element of the second planetary gearset are connected to one another in a rotationally fixed manner, whereas the second element of the second planetary gearset and the first element of the third planetary gearset are also connected rotationally fixed to one another. The third element of the second planetary gearset can be immobilized by means of the first shifting element and, by means of the second shifting element, it can be connected rotationally fixed to the drive output shaft. Finally, two of the elements of the second planetary gearset can be brought into rotationally fixed connection with one another by means of the third shifting element.

Correspondingly, in the electric vehicle transmission according to the invention the first element of the first planetary gearset is permanently connected rotationally fixed to the drive input shaft, so that the drive input shaft and the said first element of the first planetary gearset always rotate at the same speed. Furthermore, the drive output shaft and the second element of the third planetary gearset are permanently connected rotationally fixed to one another, so that the second element of the third planetary gearset and the drive output shaft also always rotate at the same speed. The third element of the first planetary gearset and the third element of the third planetary gearset are permanently immobilized, so that both the third element of the first planetary gearset and the third element of the third planetary gearset are permanently prevented from rotating. The second element of the first planetary gearset and the first element of the second planetary gearset are permanently connected rotationally fixed to one another and consequently always rotate together at the same speed. In addition, the second element of the second planetary gearset and the first element of the third planetary gearset are permanently connected rotationally fixed to one another and always rotate together.

The individual permanent rotationally fixed connections are, in the context of the invention, preferably formed in each case by way of an intermediate shaft, which can be present in one or more parts. Furthermore, in the context of the invention a particular design can be considered, in which the shaft concerned is made integrally with one or even both of the components that it connects in a rotationally fixed manner, the latter option being realized in particular when the components of the transmission that are permanently connected to one another are arranged spatially closely adjacent to one another.

Closing the first shifting element immobilizes the third element of the second planetary gearset so that it is prevented from rotating. On the other hand, if the second shifting element is changed to its closed condition, the third element of the second planetary gearset is connected rotationally fixed to the output shaft so that the third element of the second planetary gearset and the output shaft rotate together. In its closed condition the third shifting element produces a rotationally fixed connection between two elements of the second planetary gearset, and this blocks the second planetary gearset and results in its rotation as a block.

The respective permanently immobilized condition of the third element of the first planetary gearset and the third element of the third planetary gearset, and the immobilization of the third element of the second planetary gearset by means of the first shifting element, are produced in particular because the element concerned is connected rotationally fixed to a permanently fixed structural element or will be connected rotationally fixed thereto. In this case the said permanently fixed structural element is preferably a transmission housing or a component connected rotationally fixed thereto. The third element of the first planetary gearset and/or the third element of the third planetary gearset can also be made integrally with the permanently fixed structural element.

In an actuated condition of the at least functionally present third shifting element, two of the three elements of the second planetary gearset are connected rotationally fixed to one another, so that the second planetary gearset is blocked. In the context of the invention, in the actuated condition of the at least functionally present third shifting element, specifically the first element and the second element of the second planetary gearset, or the first element and the third element of the second planetary gearset, or the second element and the third element of the second planetary gearset, can be connected rotationally fixed to one another.

The design of a motor vehicle transmission according to the invention has the advantage that by means of the shifting elements, a number of different gears can be engaged between the drive input shaft and the drive output shaft, so that in the assembled condition of the motor vehicle transmission, a drive input movement of an upstream drive machine can be transmitted with different transmission ratios. Particularly when the motor vehicle transmission is combined with a drive machine in the form of an electric machine, such a combination can provide a drive unit suitable for use in an electric vehicle. By virtue of the structure of the motor vehicle transmission according to the invention this can be done with a structure that is compact overall, so that even a direct arrangement can be configured in the area of the electric vehicle in which the drive movement is produced, for example at a respective drive axle.

With the motor vehicle transmission according to the invention a first gear between the drive input shaft and the drive output shaft is engaged by closing the first shifting element, whereas on the other hand a second gear between the drive input and the drive output shafts can be engaged by actuating the second shifting element. In addition, a third gear between the drive input and the drive output shafts can be engaged by closing the third shifting element. Advantageously, this enables a suitable provision of gears of the motor vehicle transmission by correspondingly guiding the power flow via the three planetary gearsets. In this case a sequential shifting between the gears can be accomplished by changing over between two shifting elements. Thus, to change from the first gear to the second gear the first shifting element has to be opened and thereafter the second shifting element has to be actuated, whereas to change from the second gear to the third gear the second shifting element has to be opened and thereafter the third shifting element must be closed.

Preferably, the shifting elements are in the form of interlocking shifting elements, particularly preferably ones designed as unsynchronized claw-type shifting elements. Making the shifting elements in the form of interlocking shifting elements has the advantage that in an open condition of the shifting element concerned no, or only very slight, drag losses occur at the said shifting element. This improves the efficiency of the motor vehicle transmission. Alternatively, however, one or more of the shifting elements can also be interlocking shifting elements in the form of locking synchronizations. As a further alternative, one or even more of the shifting elements can be in the form of frictional shifting elements, in that case particularly preferably disk-type shifting elements. Advantageously, the shifting element concerned can then be powershifted.

In an embodiment of the invention, when it is actuated the third shifting element connects the third element of the second planetary gearset rotationally fixed to the first element of the second planetary gearset or to the second element of the second planetary gearset. In that case, the second planetary gearset is blocked in the actuated condition of the at least functionally present third shifting element, because the third element of the second planetary gearset is brought into rotationally fixed connection either with the first element of the second planetary gearset or with the second element of the second planetary gearset.

In a further development of a combination of the two above-mentioned variants, the first, second, and third shifting elements are formed by a shifting device whose coupling element can be moved to a first shift position, a second shift position, and a third shift position. Here, in its first shift position the coupling element functionally reproduces an actuated condition of the first shifting element and immobilizes the third element of the second planetary gearset. In its second shift position the coupling element functionally reproduces an actuated condition of the second shifting element and connects the third element of the second planetary gearset rotationally fixed to the output shaft. Furthermore, in its third shifting position the coupling element functionally reproduces an actuated condition of the third shifting element, since the coupling element brings the third element of the second planetary gearset into rotationally fixed connection either with the first element of the second planetary gearset or with the second element of the second planetary gearset. Reproducing the functions of the first, second, and third shifting elements by a shifting device has the advantage that by such means, the respective rotationally fixed connections can be realized in a compact manner and with a small number of structural elements.

Particularly preferable, between the shift positions the coupling element can also be moved to a neutral position in each case, such that in the individual neutral positions no coupling of the third element of the second planetary gearset takes place. Thus, when the coupling element is between the first shift position and the second shift position it is in a first neutral position, and when the coupling element is between the second and third shift positions it is in a second neutral position.

Particularly preferable, the coupling element of the shifting device is in the form of a sliding sleeve, which on a guiding tooth array in each case is guided in a rotationally fixed manner and axially displaceably on teeth, wherein the said teeth are connected rotationally fixed to the third element of the second planetary gearset. Furthermore, such a coupling element is in particular provided with at least one engagement tooth array, with which the coupling element engages at the shift position concerned in associated teeth. The teeth are in each case connected rotationally fixed to the component or components of the motor vehicle transmission which, at the individual shift position, are to be connected rotationally fixed by means of the coupling element to the third element of the second planetary gearset. Particularly preferably, the coupling element in this case has three engagement tooth arrays.

In accordance with a possible design of the invention, the output shaft is coupled to a differential gear system. In this case the said differential gear system is a transverse differential which, again preferably, is in the form of a conical gear differential. By way of the transverse differential a drive movement transmitted to the output shaft of the motor vehicle transmission is preferably distributed to drive output shafts of a drive axle of the electric vehicle. In particular, the output shaft is in this case coupled to a differential cage of the differential gear system, wherein this coupling can be effected if the output shaft is connected rotationally fixed to the differential cage or if it carries a spur gear which meshes with a drive actuator gear of the differential cage. Moreover, the differential gear system can also be a longitudinal differential by way of which drive power can be distributed to more than one drive axle.

According to an embodiment of the invention, the planetary gearsets are arranged after a connection point of the drive input shaft that serves to couple the drive input shaft to the drive machine, in the sequence of first planetary gearset, second planetary gearset, and third planetary gearset. This makes possible a suitable structure of the electric vehicle transmission according to the invention. In the context of the invention, however, in the axial direction after the connection point the planetary gearsets can be arranged in some other sequence.

In a further development of the above-mentioned embodiment, the first shifting element, the second shifting element, and the third shifting element are arranged axially between the second planetary gearset and the third planetary gearset. If the first, second, and third shifting elements are in the form of a shared shifting device, then the said shifting device is preferably positioned axially between the second planetary gearset and the third planetary gearset. In the latter case a positioning actuator by means of which the coupling element of the shifting device that functionally reproduces the first, second and third shifting elements can be moved to the first shift position, the second shift position and the third shift position, can also be positioned axially between the second and third planetary gearsets. Particularly preferably, in that case the said positioning actuator is arranged radially on the outside of the second and third planetary gearsets and is connected to the coupling element by an intermediate shifting rod.

An object of the invention is also a drive unit, which preferably is an electric axle-drive unit and which, besides an electric machine, comprises a motor vehicle transmission according to one or more of the above-described variants. A rotor of the electric machine is coupled to a drive input shaft of the motor vehicle transmission, this coupling in particular being a rotationally fixed connection between the rotor of the electric machine and a connection point of the drive input shaft. Alternatively, however, one or more intermediate gear ratio steps could be provided between the drive input shaft of the motor vehicle transmission and the rotor of the electric machine, these gear ratio steps being in the form of spur gear stages or planetary stages. In the context of the invention the electric machine in particular can be operated on the one hand as a generator and on the other hand as an electric motor.

In the context of the invention, it would also be conceivable that in the aforesaid drive unit the first planetary gearset of the motor vehicle transmission is arranged axially overlapping and radially inside the electric machine. This would produce a nested configuration of the drive unit, resulting in a compact overall structure.

A drive system that corresponds to one or more of the aforesaid variants, in particular, is part of a drive axle which is in this case provided for an electric vehicle. Preferably, the drive unit is arranged in a plane with drive output shafts which are each associated with at least one drive wheel and are coupled to the output shaft of the motor vehicle transmission. Advantageously, in that way a more compact structure of a drive axle with the drive unit can be produced, wherein the coupling between the output shaft of the motor vehicle transmission and the drive shafts of the drive axle is formed in particular by way of a differential gear system.

In the context of the invention at least one such drive axle is provided in an electric vehicle, which in particular is an electric utility vehicle. In that case the electric vehicle in particular can be an electrically powered transporter, or a light to medium-weight bus or truck.

In the context of the invention, to say that two structural elements are “connected” or “coupled” or “in connection with one another” in a rotationally fixed manner means that the said structural elements are permanently coupled, so that they cannot rotate independently of one another. Accordingly, between the said structural elements, which can be elements of the planetary gearsets and/or shafts and/or a rotationally fixed component of the transmission, no shifting element is provided, but rather, the corresponding structural elements are coupled with a fixed rotation speed ratio between them.

In contrast, if a shifting element is provided at least functionally between two structural elements, then the said structural elements are not permanently coupled to one another in a rotationally fixed manner, but rather, a rotationally fixed coupling is only formed by actuating the at least functionally intermediate shifting element. In that case actuation of the shifting element means in the context of the invention that the shifting element concerned is changed to a closed condition and consequently the rotation movements of the structural elements coupled directly thereto are equalized. In the case when the shifting element concerned is in the form of an interlocking shifting element, the structural elements connected to one another directly by it will rotate at the same rotation speed, whereas in the case of a frictional shifting element there may be rotation speed differences between the structural elements even after the shifting element has been actuated. In the context of the invention this desired, or even undesired condition is still referred to as a rotationally fixed connection between the respective structural elements.

The invention is not limited to the combination of features indicated in the principal claim or the claims that depend on it. There are further possibilities for combining individual features with one another, provided that they emerge from the claims, the description of preferred embodiments of the invention given below, or directly from the drawings. References in the claims to the drawings by the use of indexes should not be taken to restrict the protective scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous embodiments of the invention, which will be explained in greater detail below, are illustrated in the drawings, which show:

FIG. 1 : A schematic representation of an electric vehicle corresponding to a preferred embodiment of the invention;

FIG. 2 : A schematic view of a drive axle of the electric vehicle shown in FIG. 1 , with a drive unit corresponding to a preferred embodiment of the invention; and

FIG. 3 : An example of a shifting scheme of a motor vehicle transmission of the drive unit shown in FIG. 2 .

DETAILED DESCRIPTION

FIG. 1 shows a schematic representation of an electric vehicle 1, which in particular is an electric utility vehicle, such as a transporter. Besides a steerable, non-driven axle 2, the electric vehicle 1 also has a drive axle 3 in which a drive unit 4 in the form of an electric axle-drive unit is provided. Whereas in this case the vehicle axle 2 is a front axle of the electric vehicle 1, the drive axle 3 is a rear axle of the electric vehicle 1. However, alternatively, or in addition to the drive axle 3, the vehicle axle 2 could also be designed as a driven axle.

FIG. 2 shows the drive axle 3 and in this case in particular shows the drive unit 4 in greater detail, the latter of which is made in accordance with a preferred embodiment of the invention. As can be seen, the drive unit 4 consists of an electric machine 5 and a motor vehicle transmission 6, which is configured in accordance with a preferred design option of the invention. In a manner whose principle is familiar to those with a knowledge of the subject, the electric machine 5 consists of a stator 7 and a rotor 8, such that the electric machine can be operated on the one hand as a generator and on the other hand as an electric motor.

Besides a drive input shaft 9 and a drive output shaft 10, the motor vehicle transmission 6 comprises three planetary gearsets P1, P2, and P3, each consisting respectively of a first element E11 or E12 or E13, a second element E21 or E22 or E23, and a third element E31 or E32 or E33. In this case the respective first element E11, E12 or E13 of the planetary gearset P1 or P2 or P3 is a sun gear in each case, whereas the respective second element E21, E22 or E23 of the planetary gearset P1 or P2 or P3 is a planetary web. In addition, the respective third element E31, E32 or E33 of the planetary gearset P1 or P2 or P3 is a ring gear of the planetary gearset P1 or P2 or P3 of the planetary gearset concerned.

On the respective planetary web of the planetary gearset concerned there is in each case at least one planetary gearwheel which is mounted to rotate, which meshes with the respective sun gear and also the ring gear of the respective planetary gearset P1 or P2 or P3. Thus, the planetary gearsets P1, P2 and P3 are in this case all minus-planetary gearsets.

In the context of the invention, however, it can also be considered to make one or more of the planetary gearsets P1 to P3 as a plus-planetary gearset, and in that case, compared with their design as minus-planetary gearsets, the respective second element E21 or E22 or E23 will be a ring gear and the respective third element E31 or E32 or E33 will be the planetary web in each case. In addition, the stationary gear ratio of a respective planetary gearset made as a plus-planetary gearset must be increased by one compared with a design as a minus-planetary gearset. In a plus-planetary gearset, on the planetary web concerned at least one pair of planetary gearwheels are mounted to rotate, of which pair one planetary gearwheel meshes with the sun gear and one meshes with the ring gear, and the planetary gearwheels of the at least one pair of planetary gearwheels also mesh with one another.

In the present case the first element E11 of the first planetary gearset P1 is connected rotationally fixed to the drive input shaft 9, which is also connected rotationally fixed to the rotor 8 of the electric machine 5. Thus, the first element E11 of the first planetary gearset P1 and the rotor 8 are connected rotationally fixed to one another via the drive input shaft 9, so that the said first element E11 and the rotor 8 always rotate at the same rotation speed. In the context of the invention the first element E11 of the first planetary gearset P1 can be made integrally, as one piece with the drive input shaft 9. The second element E21 of the first planetary gearset P1 is permanently connected rotationally fixed to the first element E12 of the second planetary gearset P2, so that these two elements E21 and E12 also always rotate at the same rotation speed. Likewise, the second element E22 of the second planetary gearset P2 and the first element E13 of the third planetary gearset P3 are permanently connected rotationally fixed to one another, so that the second element E22 of the second planetary gearset P2 and the first element E13 of the third planetary gearset P3 always rotate together. The respective rotationally fixed connections in this case are preferably each formed by way of a respective intermediate shaft.

As can also be seen in FIG. 2 , both the third element E31 of the first process gearset P1 and the third element E33 of the third process gearset P3 are each immobilized on a permanently fixed structural element 11 and thus are each permanently prevented from rotating. In this case the said structural element 11 is preferably a transmission housing of the motor vehicle transmission 6, a part of such a transmission housing, or a component connected thereto in a rotationally fixed manner. In the context of the invention, in this case the third element E31 of the first planetary gearset P1 and/or the third element E33 of the third planetary gearset P3 can be made integrally with the structural element 11.

The second element E23 of the third planetary gearset P3 is connected rotationally fixed to the output shaft 10 of the motor vehicle transmission 6, so that the second element E23 of the third planetary gearset P3 and the output shaft 10 always rotate together. Accordingly, the second element E23 of the third planetary gearset P3 can even be made integrally with the output shaft 10.

Besides the second element E23 of the third planetary gearset P3, the output shaft 10 is also permanently connected rotationally fixed to a differential cage 12 of a differential gear system. This differential gear system 13 is in the form of a conical gear differential, which in a manner whose principle is known to those familiar with the subject, distributes a drive power passing into the differential cage 12 by way of the output shaft 10, to drive output shafts 14 and 15 of the drive axle 3. In driving connection with the drive output shafts 14 and 15, there is a respective drive wheel 16 or 17 of the drive axle 3.

In the motor vehicle transmission 6 a shifting device 18 is also provided, by means of which various couplings with interlock can be effected. Here, the shifting device 18 is an unsynchronized shifting device which reproduces the function of three shifting elements A, B and C, as indicated in FIG. 2 . The shifting device 18 comprises a coupling element 19 which is designed in the form of a sliding sleeve and is guided on a guiding tooth array 20, rotationally fixed and axially displaceably on teeth 21. In this case the said teeth 21 are connected rotationally fixed to the third element E32 of the second planetary gearset P2. In addition, the coupling element 19 is provided with first engagement teeth 22, second engagement teeth 23, and third engagement teeth 24, and can be moved by an associated positioning actuator 25 to three different shift positions and two intermediate neutral positions. The positioning actuator 25 is preferably an electro-mechanical actuator.

In a first shift position, the coupling element 19 of the shifting device 18 engages with the engagement teeth 22 in a tooth array 26 which is connected rotationally fixed to the structural element 11. Thereby, an actuated condition of the shifting element A is functionally obtained, in which the third element E32 of the second planetary gearset P2 is fixed by way of the coupling element 19 to the rotationally fixed structural element 11 and thus prevented from rotating. This first shift position of the coupling element 19 is the one shown in FIG. 2 .

From the first shift position, the coupling element 19 of the shifting device 18 can be moved by the positioning actuator 25 to a first neutral position, in which the meshing engagement between the engagement teeth 22 and the teeth 26 is released and in which the third element E32 of the second planetary gearset P2 is decoupled. From the first neutral position further axial movement, besides changing from the first shift position, also changes the coupling element 19 to a second shift position in which the engagement teeth 23 mesh with teeth 27. These teeth 27 are connected rotationally fixed to the third element E33 of the third planetary gearset P3 and the output shaft 10. The result of that engagement is that the third element E32 of the second planetary gearset P2 is connected rotationally fixed by way of the coupling element 19 to the output shaft 10. Thus, this second shift position of the coupling element 19 corresponds functionally to an actuated condition of the shifting element B.

From the second shift position, the coupling element 19 can be moved by the positioning actuator 25 on the one hand in one axial direction back to the first neutral position, or alternatively in the other axial direction to a second neutral position in which the third element E32 of the second planetary gearset P2 is again completely decoupled.

The positioning actuator 25 can move the coupling element 19 from the second neutral position, on the one hand back to the second shift position and on the other hand, by an axial movement in the opposite direction, to a third shift position. In this third shift position, with its engagement teeth 24 the coupling element 19 engages in teeth 28, which are permanently connected rotationally fixed to the second element E22 of the second planetary gearset P2 and the first element E13 of the third planetary gearset P3. This reproduces the actuated condition of the shifting element C, in which the third element E32 of the second planetary gearset P2 is connected rotationally fixed to the second element E22 of the second planetary gearset P2 and to the first element E13 of the third planetary gearset P3. Owing to the rotationally fixed connection between the second element E22 and the third element E32 of the second planetary gearset P2, this results in blocking of the second planetary gearset P2 which then rotates as a block.

In the present case, the drive unit 4 is arranged parallel to the drive axle 3 and in a plane with the drive output shafts 14 and 15, so that the drive unit 4 is arranged axially between the drive wheels 16 and 17. In this case the electric machine 5 is arranged axially adjacent to the drive wheel 17, so that the first planetary gearset P1 of the motor vehicle transmission 6 is positioned axially at the level of, and radially inside the stator 7 of the electric machine 5. Axially after the first planetary gearset P1, there follow first the second planetary gearset P2 and then the third planetary gearset P3 and the differential 13, wherein the latter, together with the planetary gearsets P1 to P3, can be accommodated in a transmission housing of the motor vehicle transmission 6.

The shifting device 18 is positioned axially between the second planetary gearset P2 and the third planetary gearset P3, so that in this case the shifting device 18 is specifically arranged between the third planetary gearset P3 and a radial connection of the teeth 26 on the structural element 11. The positioning actuator 25 of the shifting device 18 is positioned axially also between the third planetary gearset P3 and the said radial connection and radially around the two planetary gearsets P2 and P3, in such manner that the positioning actuator 25 is coupled to the coupling element 19 by way of a shifting rod 29.

Furthermore, FIG. 3 shows an example shifting scheme for the motor vehicle transmission 6 in FIG. 2 . It can be seen that in the motor vehicle transmission 6 a first gear G1, a second gear G2, and a third gear G3 can be engaged, and in the table of FIG. 3 an X is used in each case to indicate which of the shifting elements A, B, and C reproduced by the shifting device 18 has to be actuated. As described earlier, to produce an actuated condition of the shifting element A or B or C concerned, the coupling element 19 is moved to the respectively associated shift position.

The first gear G1 between the drive input shaft 9 and the drive output shaft 10 is obtained by actuating the shifting element A. Accordingly, in that case the third element E32 of the second planetary gearset P2 is fixed by the coupling element 19 to the structural element 11.

In contrast, to engage the second gear G2 the shifting element B has to be functionally actuated, so that the third element E32 of the second planetary gearset P2 is now connected rotationally fixed to the output shaft 10. Accordingly, to shift from the first gear G1 to the second gear G2 the coupling element 19 of the shifting device 18 has to be moved from the first shift position (actuated condition of the shifting element A), through the first neutral position and to the second shift position (actuated condition of the shifting element B).

Finally, the third gear G3 of the motor vehicle transmission 6 is engaged by functionally actuating the shifting element C. Correspondingly, in the shifting device 18 the coupling element 19 has to be moved to the shift position in which the engagement teeth 24 mesh with the teeth 28. Thereby, the third element E32 of the second planetary gearset P2 is connected rotationally fixed to the second element E22 of the second planetary gearset P2 so that the second planetary gearset P2 is blocked. To shift from the second gear G2 to the third gear G3, the coupling element 19 of the shifting device 18 has to be moved from the second shift position (actuated condition of the shifting element B) through the second neutral position to the third shift position (actuated condition of the shifting element C). During respective gearshifts between the gears G1 to G2 and G2 to G3, the requisite synchronized rotation speeds at the coupling element 19 are set by means of the electric machine 5 by corresponding rotation speed regulation.

By virtue of the design of a motor vehicle transmission according to the invention, different gears can be engaged by compact means.

INDEXES

-   -   1 Electric vehicle     -   2 Vehicle axle     -   3 Drive axle     -   4 Drive unit     -   5 Electric machine     -   6 Motor vehicle transmission     -   7 Stator     -   8 Rotor     -   9 Drive input shaft     -   10 Drive output shaft     -   11 Structural element     -   12 Differential cage     -   13 Differential gear system     -   14 Drive output shaft     -   15 Drive output shaft     -   16 Drive wheel     -   17 Drive wheel     -   18 Shifting device     -   19 Coupling element     -   20 Guiding tooth array     -   21 Teeth     -   22 Engagement teeth     -   23 Engagement teeth     -   24 Engagement teeth     -   25 Positioning actuator     -   26 Teeth     -   27 Teeth     -   28 Teeth     -   29 Shifting rod     -   P1 First planetary gearset     -   P2 Second planetary gearset     -   P3 Third planetary gearset     -   E11 First element of the first planetary gearset     -   E21 Second element of the first planetary gearset     -   E31 Third element of the first planetary gearset     -   E12 First element of the second planetary gearset     -   E22 Second element of the second planetary gearset     -   E32 Third element of the second planetary gearset     -   E13 First element of the third planetary gearset     -   E23 Second element of the third planetary gearset     -   E33 Third element of the third planetary gearset     -   A Shifting element     -   B Shifting element     -   C Shifting element     -   G1 First gear     -   G2 Second gear     -   G3 Third gear 

The invention claimed is:
 1. A motor vehicle transmission for an electric vehicle, comprising: a drive input shaft configured for connection to a drive machine; a drive output shaft; and a first planetary gearset, a second planetary gearset, and a third planetary gearset, each of which comprises a first element, a second element, and a third element in a form, respectively, of a sun gear, a planetary web, and a ring gear; wherein at least functionally a first shifting element, a second shifting element, and a third shifting element are provided, and wherein the first element of the first planetary gearset is connected rotationally fixed to the drive input shaft and the second element of the third planetary gearset is connected rotationally fixed to the drive output shaft; wherein: the third element of the first planetary gearset is immobilized, the third element of the third planetary gearset is immobilized, the second element of the first planetary gearset and the first element of the second planetary gearset are connected rotationally fixed to one another, the second element of the second planetary gearset and the first element of the third planetary gearset are connected rotationally fixed to one another, the third element of the second planetary gearset can be immobilized by means of the first shifting element and connected rotationally fixed to the drive output shaft by means of the second shifting element, and two of the elements of the second planetary gearset can be brought into connection with one another by means of the third shifting element.
 2. The motor vehicle transmission according to claim 1, wherein: a first gear between the drive input shaft and the drive output shaft is obtained by closing the first shifting element; a second gear between the drive input shaft and the drive output shaft is obtained by actuating the second shifting element; and a third gear between the drive input shaft and the drive output shaft is obtained by closing the third shifting element.
 3. The motor vehicle transmission according to claim 1, wherein the shifting elements are configured as interlocking shifting elements.
 4. The motor vehicle transmission according to claim 3, wherein the shifting elements are configured as unsynchronized claw-type shifting elements.
 5. The motor vehicle transmission according to claim 1, wherein when the third shifting element is actuated, it connects the third element of the second planetary gearset rotationally fixed to the first element of the second planetary gearset or to the second element of the second planetary gearset.
 6. The motor vehicle transmission according to claim 5, wherein the first shifting element, the second shifting element, and the third shifting element are formed by a shifting device having a coupling element configured to be positioned in a first shift position, a second shift position, and a third shift position, wherein: in the first shift position the coupling element functionally reproduces an actuated condition of the first shifting element and immobilizes the third element of the second planetary gearset; in the second shift position the coupling element functionally reproduces an actuated condition of the second shifting element and connects the third element of the second planetary gearset rotationally fixed to the drive output shaft; and in the third shift position the coupling element functionally reproduces an actuated condition of the third shifting element and connects the third element of the second planetary gearset rotationally fixed to the first element of the second planetary gearset or to the second element of the second planetary gearset.
 7. The motor vehicle transmission according to claim 6, wherein a positioning actuator, by means of which the coupling element of the shifting device that functionally reproduces the first shifting element, the second shifting element, and the third shifting element can be moved to the first shift position, the second shift position, and the third shift position, is located axially between the second planetary gearset and the third planetary gearset.
 8. The motor vehicle transmission according to claim 1, wherein the drive output shaft is coupled to an input side of a differential gear system.
 9. The motor vehicle transmission according to claim 1, wherein the planetary gearsets are arranged after a connection point of the drive input shaft configured to couple the drive input shaft to the drive machine, in a sequence first planetary gearset, second planetary gearset, and third planetary gearset.
 10. The motor vehicle transmission according to claim 9, wherein the first shifting element, the second shifting element and the third shifting element are arranged axially between the second planetary gearset and the third planetary gearset.
 11. A drive unit for an electric vehicle, the drive unit comprising an electric machine and a motor vehicle transmission according to claim 1, wherein a rotor of the electric machine is coupled to the drive input shaft of the motor vehicle transmission.
 12. The drive unit according to claim 11, wherein the first planetary gearset of the motor vehicle transmission is positioned axially at the level of and radially inside the electric machine.
 13. A drive axle for an electric vehicle, the drive axle comprising a drive unit having an electric machine and a motor vehicle transmission according to claim 1, wherein a rotor of the electric machine is coupled to the drive input shaft of the motor vehicle transmission.
 14. The drive axle according to claim 13, wherein the drive unit is arranged in a plane with drive output shafts, each of the drive output shafts associated with at least one drive wheel and coupled to the drive output shaft of the motor vehicle transmission.
 15. An electric vehicle comprising at least one drive axle the at least one drive axle comprising a drive unit having an electric machine and a motor vehicle transmission according to claim 1, wherein a rotor of the electric machine is coupled to the drive input shaft of the motor vehicle transmission. 